The distribution of all known Cambrian echinoderm taxa, encompassing both articulated specimens and taxonomically diagnostic isolated ossicles, is documented for the first time. The database described by 2011 comprises 188 species recorded from 65 formations from around the world. Formations that have yielded articulated echinoderms are unequally distributed in space and time. Only Laurentia and West Gondwana provide reasonably complete records at the resolution of Stage. The review of the biogeographical distributions of the eight major echinoderm clades shows that faunas from Laurentia and Northeast Gondwana (China and Korea) are distinct from those of West Gondwana and Southeast Gondwana (Australia); other regions are too poorly sampled to make firm palaeobiogeographical statements. Analysis of alpha diversity (species per formation) shows that diversity rose initially to Cambrian Stage 5, declined into Guzhangian and Paibian before returning to Stage 5 levels by the end of the Cambrian. This pattern is replicated in Laurentia and West Gondwana. We show that taxonomically diagnostic ossicles found in isolation typically occur significantly earlier than the first articulated specimens of the same taxa and provide important information on the first occurrence and palaeobiogeographical distribution of key taxa, and of the phylum as a whole.Supplementary material:Articulated Cambrian echinoderms and Isolated plates of Cambrian echinoderms are provided at:http://www.geolsoc.org.uk/SUP18668

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The focus of this paper is to re-evaluate the age and the paleogeographical significance of the Heraultia Limestone in the light of recent advances in SSF systematic and biostratigraphy. Reassessed assemblage is dominated by molluscs (helcionellids, ?polyplacophors and other problematic taxa), and abundant orthothecid hyoliths, problematic tubes; few problematica are also present. Twenty-eight species and three morphotypes are described. Two species and one genus are new (Obscurania tormoi Devaere, sp. nov.; Alaconcha Devaere, gen. nov. and Alaconcha rugosa Devaere, sp. nov.), seven are reported for the first time. Among previously mentionned species, 13 are reassigned, 7 confirmed, and 9 unrecovered from the studied sampled. The global stratigraphic range of each species is established based on updated inventory of known occurrences. It argues for a Terreneuvian (Nemakit-Daldynian/Tommotian according to the Siberian stratigraphic chart) age of the microfossil assemblage. The Watsonella crosbyi-Oelandiella korobkovi Interval Zone is defined and is correlated with base of Cambrian Stage 2 (Tommotian) of Siberia, China, Mongolia, and Avalonia. The Northern Montagne Noire would accordingly witness for one of the earliest, isolated but consequent Tommotian carbonate-platform on the Western Gondwana margin. As a result, present tectonic and palaeogeographic models have to be emended, and factors that favored such isolated platforms should be further investigated.

International audienceThe volcanism hosted by the Ediacaran–Terreneuvian Canaveilles Group of the Eastern Pyrenees displays two distinct geochemical affinities: (1) metabasites of the Nyer and Olette formations reflect the emplacement of a tholeiitic magmatism linked to extensional conditions, whereas (2) subsequent felsic and calc-alkaline magmatic rocks marking the top of the Olette Formation and forming the overlying Fabert and Finestrelles members represent Cadomian magmatic events. Based on U–Pb zircon dating constraints, palaeotopographic relationships linked to onlap geometries and distance from vent sources, three volcanosedimentary edifices can be distinguished, the so-called Tregurà (ca. 565–552 Ma), Cap de Creus (ca. 558 Ma) and Coll d’Ares (ca. 542–532 Ma) edifices. The top of their palaeoreliefs recorded locally the nucleation of centres of microbial carbonate productivity (Puig Sec Member) linked to synsedimentary tilting and karstification. Throughout West Gondwana, the presence of carbonate production across the Ediacaran–Cambrian transition is exclusively located in back-arc settings (Central-Iberian Zone) and areas far from the Cadomian subduction trench and devoid of significant terrigenous input, such as those reported in the Eastern Pyrenees and the neighbouring Montagne Noire

A comprehensive review and phylogenetic analysis of genera and species presently assigned to the rhynchonelliform superfamily Nisusioidea and family Nisusiidae suggests that this short‐lived but important group of brachiopods first appeared in peri‐Gondwana during the second half of the Cambrian Series 2, before going extinct by the end of Drumian times. Nisusiides achieved their maximum morphological disparity and geographical distribution during the Wuliuan Age, and Laurentia was probably the major centre of their dispersal. A new phylogenetic analysis suggests an early separation of the lineages of spinose and non‐spinose nisusiids. The non‐spinose nisusiids probably evolved in Laurentia by the end of Cambrian Series 4. The new nisusiid genus Bellistrophia is described. The new species Nisusia multicostata represents the first documented rhynchonelliform (kutorginide) brachiopod from the Miaolingian (Drumian) of the Alborz Mountains, Iran.

More than 285 specimens of Conotheca subcurvata with three-dimensionally preserved digestive tracts were recovered from the Terreneuvian (early Cambrian) Heraultia Limestone of the northern Montagne Noire, southern France. They represent one of the oldest occurrences of such preserved guts. The newly discovered operculum of some complete specimens provides additional data allowing emendation of the species diagnosis. Infestation of the U-shaped digestive tracts by smooth uniseriate, branching to anastomosing filaments along with isolated botryoidal coccoids attests to their early, microbially mediated phosphatisation. Apart from taphonomic deformation, C. subcurvata exhibits three different configurations of the digestive tract: (1) anal tube and gut parallel, straight to slightly undulating; (2) anal tube straight and loosely folded gut; and (3) anal tube straight and gut straight with local zigzag folds. The arrangement of the digestive tracts and its correlation with the mean apertural diameter of the specimens are interpreted as ontogenetically dependent. The simple U-shaped gut, usually considered as characteristic of the Hyolithida, developed in earlier stages of C. subcurvata, whereas the more complex orthothecid type-3 only appears in largest specimens. This growth pattern suggests a distinct phylogenetic relationship between these two hyolith orders through heterochronic processes.

Middle to Upper Ordovician ironstone and associated sedimentary rocks of the West Asturian‐Leonese and Cantabrian tectonostratigraphic zones, Spain, provide new information regarding the Palaeozoic Fe cycle and the palaeoceanography of the Rheic Ocean. Examination of drill cores and outcrops indicates the southeastern margin of this narrow seaway was a dynamic continental shelf where upwelling of ferruginous seawater and storm currents controlled lithofacies character. Parasequence composition and stacking relationships suggest ironstone accumulated during marine transgression as accommodation increased from lowstand conditions. Proximal parasequences record aggradation from deep subtidal to shoreface environments. Hummocky cross‐stratified sandstone and organic‐rich siltstone grade upwards into swaley cross‐stratified sandstone and granular Fe‐silicate‐rich ironstone capped by a flooding surface. Distal parasequences were deposited below storm wave base on the distal shelf and are composed of variably bioturbated organic‐rich siltstone with thin Fe‐chlorite and phosphorite layers. These differences in parasequence character define two different ironstone factories where Fe was concentrated and precipitated in sediment. Lithofacies associations support an emerging model for ironstone deposition where coastal upwelling delivered and stimulated the precipitation of Fe within shelf sediment. This notion provides further evidence for the development of intermittent anoxic water masses in an Ordovician ocean that was near the threshold of becoming fully ventilated. This style of Fe delivery probably represents a tipping point in the oxygenation history of the Phanerozoic oceans and is a throwback to the Precambrian when widespread anoxia allowed hydrothermal Fe to concentrate in the global ocean. New data suggest that minor extinction events punctuating the Great Ordovician Biodiversification Event may be traced to these anoxic waters, which in addition to Fe, were also enriched in biologically toxic, redox sensitive trace elements. Conversely, precipitation of upwelling‐related ironstone may have helped sequester these trace elements, providing a negative feedback response that would aid post‐extinction recovery.

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